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Information Circular 9123 



Placer Gold Deposits of the 
Eagle Trough, Upper Yukon Ri 
Region, Alaska 



By James C. Barker 





UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 



huM 




:i:L Bureau of Mines Information Circular/1986 



Placer Gold Deposits of the 
Eagle Trough, Upper Yukon River 
Region, Alaska 



By James C. Barker 



<5^ 




UNITED STATES DEPARTMENT OF THE INTERIOR 



As the Nation's principal conservation agency, the Department of the Interior has 
responsibility for most of our nationally owned public lands and natural resources. This 
includes fostering the wisest use of our land and water resources, protecting our fish 
and wildlife, preserving the environment and cultural values of our national parks and 
historical places, and providing for the enjoyment of life through outdoor recreation. 
The Department assesses our energy and mineral resources and works to assure that 
their development is in the best interests of all our people. The Department also has 
a major responsibility for American Indian reservation communities and for people who 
live in island territories under U.S. administration. 



T 






Library of Congress Cataloging-in-Publication Data 



Barker, James C. 

Placer gold deposits of the Eagle Trough, upper Yukon River region, 
Alaska. 



(Information circular/United States Department of the Interior, Bureau of Mines; 9123 ) 

Bibliography: p. 

Supt. of Docs, no.: I 28.27: 

1. Gold mines and mining— Yukon River Watershed (Yukon and Alaska) 2. Placer 
deposits— Yukon River Watershed (Yukon and Alaska) I. Title. II. Series: Information 
circular (United States. Bureau of Mines) ; 9123. 

TN295.U4 [TN423.A7] 622 s [553.4T097984] 86-600295 



CONTENTS 



in 



Page 

Abstract 1 

Introduction 2 

Acknowledgments 2 

Access 2 

Land status and ownership 2 

Physiographic features 2 

Geology 5 

Geological terranes 5 

Geology of Tertiary sediments 5 

Tintina Fault trench 7 

Mineral production and history 7 

Sam Creek 7 

Willow Creek 7 

Rosebud Creek 7 

Grouse Creek 9 

Webber Creek 9 

Surprise Creek 9 

Irish Gulch 9 

Eagle Creek 9 

Drayham Creek 9 

Dome Creek 9 

Colorado Creek 9 

Alder Creek 9 

Fourth of July Creek 9 



Page 

Ruby Creek io 

Sawyer Gulch 10 

Coal Creek 10 

Boulder Creek 10 

Mineral Creek 10 

Woodchopper Creek 10 

Iron Creek 11 

Thanksgiving Creek 11 

Nugget Creek 11 

Ben Creek 11 

Bonanza Creek 11 

Gold content in panned concentrates 11 

Mode of occurrence and character of placer gold . . 14 
Significance of Bonanza Creek lineament zone for 

placer gold 16 

Other locations containing gold 17 

Platinum association 17 

Discussion and recommendations 17 

Conclusions 19 

References 20 

Appendix A.— Gold in heavy-mineral 

concentrates 21 

Appendix B.— Sample identification key 23 



ILLUSTRATIONS 

1. Map of study area 3 

2. Dredge on Woodchopper Creek 4 

3. Rolling forested terrain of upper Woodchopper Creek 4 

4. Study area general geology and gold occurrences 6 

5. Coal Creek area 8 

6. Bonanza Creek placer drill hole location map 12 

7. Panned sample location map 13 

8. Histogram of gold content in 159 panned concentrates 14 

9. Textures of placer gold 15 

10. Sample locations 50 through 56, Washington Creek 18 

TABLES 



1. Mineralogic analysis of Woodchopper Creek placer concentrate. 

2. Fineness of upper Yukon River region gold samples 



10 
16 



UNITS OF MEASURE ABBREVIATIONS USED IN THIS REPORT 



ft 


foot 


ft' 


square foot 


g 


gram 


in 


inch 


lb 


pound 


mg 


milligram 


mi 2 


square mile 



ppm 


part per million 


tr oz 


troy ounce 


tr oz/st 


troy ounce per short ton 


tr oz/yr 


troy ounce per year 


yd 


yard 


yd 3 


cubic yard 


yr 


year 



PLACER GOLD DEPOSITS OF THE EAGLE TROUGH, UPPER YUKON 

RIVER REGION, ALASKA 

By James C. Barker 1 



ABSTRACT 

Gold placer deposits along the upper Yukon River, in the region between the river 
villages of Circle and Eagle, were investigated by the Bureau of Mines. The investiga- 
tion was conducted intermittently between 1976 and 1985 as part of an evaluation of 
mineral resources on lands proposed for inclusion in the National Park System. At least 
230,000 troy ounces (tr oz) of gold has been produced in the region, principally from 
Woodchopper, Coal, and Fourth of July Creeks. 

The placers are underlain by, or occur downstream of, early Tertiary sediments that 
have been deposited in the Eagle Trough. Strike-slip displacement along the Tintina 
Fault is responsible for creation of the trough and may have been a factor in the forma- 
tion of the present placers. Placers were found to have a close spatial correlation to 
certain altered fault lineaments of the Tintina Fault trench. Placer concentrates con- 
tain several different textural forms of gold, suggesting multiple origins. 

Geological studies and a survey of 162 panned concentrates throughout the region 
indicated previously unreported sites of placer gold, and potential exists for the discovery 
of additional placer and lode gold. Because of nearly continuous soil and vegetation cover, 
further evaluation of the region will require subsurface sampling. 



'Supervisory physical scientist, Alaska Field Operations Center, Fairbanks, AK. 



INTRODUCTION 



The Bureau conducted field studies on portions of the 
upper Yukon River drainage (fig. 1) intermittently between 
1976 and 1981. Because of inclusion of the Eagle Trough 
area into the National Park System under the authority 
of the Alaska Native Claims Settlement Act (Public Law 
92-203), and the need for minerals information on adjoin- 
ing land managed by the Bureau of Land Management in 
the Steese and White Mountains areas, data gathering, 
analysis, and mineral resource evaluation continued 
through 1985. 

Most of the approximately 230,000 tr oz of placer gold 
production from the upper Yukon River region (fig. 2) was 
produced prior to 1950. The most comprehensive published 
accounts of placer mining in the region are those by Mer- 
tie in 1937, 1938, and 1942 {11-13)} Other investigators who 
have contributed observations and data on these placer 
deposits include Brooks (5), Prindle (17), and Smith (19). 

Reconnaissance-level geologic mapping was first com- 
piled by Mertie (12-13). More recent work by Payne (15), 
Tempelman-Kluit (21), and Brabb (4) has contributed to the 
knowledge of geology in the area. 



Previous work in the region by Sainsbury (18), sug- 
gesting possible associations of the placer gold to bedrock 
sources, partially led to this study. The work by Sainsbury 
raised fundamental questions regarding the previous 
assumption that placer gold in the region is derived from 
low-grade auriferous Tertiary gravels. Sainsbury compiled 
an unpublished manuscript in 1972 (18) that dealt in part 
with the area of interest. His conclusions, coupled with the 
evidence compiled by the Bureau, indicate that new explora- 
tion targets for gold exist which to date have not been tested. 

The upper Yukon River region is an area of complex 
geology and nearly continuous vegetative and soil cover. 
This report presents observations and data pertaining to 
the distribution of gold in the region and a discussion of 
the potential host and geologic controls for yet undiscovered 
deposits of both lode and placer gold. In an area such as 
the upper Yukon River region, this type of subjective 
evaluation is one way a reconnaissance-level study with 
limited funding can provide an estimate of mineral develop- 
ment potential for the purpose of land-use planning. 



ACKNOWLEDGMENTS 



The author would like to acknowledge the helpful in- 
formation and hospitality provided by Mr. Del Booth, 
manager of the Coal Creek placer operation, a tributary of 
the upper Yukon River, who made possible the investiga- 
tion there. Similarly, Mr. Joe Volger, a local mine owner, 
provided access to the nearby Woodchopper Creek drainage. 



Suggestions and advice were also provided by C. Sainsbury, 
geologist, Air Samplex, Inc., Denver, CO. X-ray diffraction 
and petrographic studies were contributed by T. Mowatt and 
W. Roberts, geologists, and W. Gnagy, petrologist, all 
formerly with the Bureau's analytical laboratory in Juneau, 
AK. 



ACCESS 



The upper Yukon River region is most accessible near 
the Yukon River, which is navigable by moderate-size 
barges. Light river craft can also ascend the Charley River 
to the vicinity of Drayham Creek. Elsewhere, the region 



is typified by dense brush and forest cover, which makes 
overland travel exceedingly difficult. Helicopter service, 
available at Circle, AK, was utilized where river access was 
impractical. 



LAND STATUS AND OWNERSHIP 



The upper Yukon River region (fig. 1) is included within 
the Yukon-Charley Rivers National Park and is ad- 
ministered by the National Park Service from its head- 
quarters in Eagle, AK. The park was established by passage 
of the Alaska National Interest Land Conservation Act of 



1980 and is withdrawn from mineral exploration and en- 
try under the Mining Law of 1872. Previously existing 
mineral rights are still valid on the principal gold placer 
creeks, and a mineral patent has been issued within the 
valley of Woodchopper Creek. 



PHYSIOGRAPHIC FEATURES 



Much of the topography along the upper Yukon River 
consists of low, rounded, forested hills. Elevations range 



'Italic numbers in parentheses refer to items in the list of references 
preceding the appendixes at the end of this report. 



from 900 ft along the river to hilltops at about 3,000 ft. 
However, in the area to the south (referred to later in this 
report as the Tanana Uplands crystalline terrane), the 
topography is much more rugged, with elevations ranging 
up to 5,784 ft (the elevation of Twin Mountain). 




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FIGURE 2.— Dredge on Woodchopper Creek. 




FIGURE 3.— Rolling forested terrain of upper Woodchopper Creek. Bedrock is Tertiary-age sediments. Mountains of Tanana Upland 
crystalline terrane are in background. 



Some limited Pleistocene glaciation was reported by 
Pew6 (16) to have occurred at the higher elevations; 
however, no glaciers are present. Elevations exceeding 
4,000 ft are believed to have supported early Pleistocene 
valley glaciers and small icecaps (24). Auriferous gravels 
occur at elevations between 900 and 1,800 ft. No evidence 
was seen during this study to indicate glacial influence on 
the formation or preservation of placer deposits in the area. 

Below 3,000 ft, very little bedrock outcrops, except along 
the major rivers. Smaller streams often lack float rock and 
have poorly defined channels choked with muskeg and 
vegetation, especially in areas underlain by Tertiary 



mudstone. Bedrock in the upper Yukon River region is fur- 
ther masked by discontinuous permafrost soils. Most placer 
mining has encountered permafrost. Early mining ventures 
consisted of drift mining in frozen ground. Dense vegeta- 
tion, tundra and muskeg ground mat, and wind-blown loess 
cover bedrock at all lower elevation levels (fig. 3). 

High bench deposits of alluvial and glaciofluvial gravels 
typically mantle the slopes above some stream valleys, in- 
dicating relatively recent but undated regional uplift. The 
Yukon River once flowed through a wide, gently inclined 
valley, into which it has now incised a canyon 700 to 800 
ft below its former channels (13). 



GEOLOGY 



GEOLOGICAL TERRANES 

There are four major geological terranes underlying or 
adjoining the upper Yukon River region (fig. 4). Lying north 
of the Tintina Fault trench are stratigraphic sequences of 
mostly marine Paleozoic and Precambrian age sedimentary 
rocks (including the Tindir Group), with minor mafic 
volcanics and associated red beds. These rocks have been 
recently included with the Yukon tectonostratigraphic ter- 
rane by Jones (10). East of the Kandik River, these rocks 
have been exposed by uplift that began in the early Ter- 
tiary and resulted in the formation of the Nation Arch, as 
described by Miller (14). 

Overlying the older rocks of the Yukon terrane is a rem- 
nant succession of Triassic to Cretaceous clastic sediments. 
These rocks have been mapped as a terrane of deformed up- 
per Mesozoic flysch (10) and lie in a wide trough that 
roughly parallels the Kandik River valley. This unit is also 
referred to as the Kandik Group by Brabb (4) and gener- 
ally consists of a monotonous sequence of sandstone, 
graywacke, quartzite, and argillite that is underlain by a 
carbonaceous shale. 

South of the Tintina Fault trench are metasedimentary 
and igneous rocks of the Tanana Uplands crystalline ter- 
rane. Phyllites, quartz-mica schist, quartzites, and gneisses 
are intruded by undated granitic rocks and pegmatites. The 
intrusions are probably Mesozoic in age, based on 
similarities to the Circle Hot Springs quartz monzonite 
pluton to the west, which was dated at 71 million yr by 
potassium-argon mica and whole-rock, and rubidium- 
strontium whole-rock methods (22). Some units of metamor- 
phosed greenstones and serpentiruzed mafic and ultramafic 
complexes of the 70-mile mafic terrane, as defined by Jones 
(10), are also included in the Tanana Uplands crystalline 
terrane, but are not differentiated on figure 4. 

The fourth and youngest terrane shown on figure 4 is 
composed of Late Cretaceous (?) to early Tertiary age non- 
marine, coal-bearing sediments that lie in the Eagle Trough 
and align with the Tintina Fault trench. 

GEOLOGY OF TERTIARY SEDIMENTS 

A sequence of conglomerate, sandstone, mudstone, 
lignite, and carbonaceous sediments extends in a west- 
northwest trend up to 15 miles wide (fig. 4). The Tertiary 



sediments lie in the Eagle Trough as described by Miller 
(14) and are reported by Brabb (4) to be 3,000 to 10,000 ft 
thick. They are generally characterized by a subdued 
topography and complexly faulted and folded structure due 
to the proximity of the Tintina Fault. 

The conglomerates are generally composed of well- 
rounded white, green, and rarer black chert, quartz, and 
quartzite clasts in a sandy matrix with minor carbonate 
(identified as ankerite on Sam Creek). Clasts rarely exceed 
3 in across. Induration varies widely from resistant, cliff- 
forming units on Washington and Sam Creeks, to more com- 
mon weakly cemented gravel found elsewhere. 

Within the Tertiary section are local units of poorly 
sorted and consolidated conglomerate that contain 
subrounded clasts up to 16 in. in diameter. Unlike the more 
common well-rounded chert congolmerates, these local units 
contain clasts of high-grade metamorphic rocks, intrusive 
rocks, vein quartz, and arkosic sandstone. The age of this 
limited, higher energy sedimentation is unknown, 
althought it is likely older than the lower energy environ- 
ment that produced stratified, well-rounded and sorted 
sediments. Southeast of the study area, in the vicinity of 
Eagle, Mertie (13) reports conglomerate with similar high- 
grade metamorphic and igneous clasts at the base of the 
Tertiary section. This is also apparently the case on Iron 
Creek, a tributary to Woodchopper Creek, but not on Coal 
and Boulder Creeks. On Washington Creek, the local higher 
energy conglomerate appears to lie above mudstone and 
lignite. The contrasting compositions of the two con- 
glomerate units indicates that multiple sources of detritus 
filled the Eagle Trough. These sources included the 
Paleozoic and Precambrian terrane to the north, during the 
development of the early Tertiary Nation Arch, and the 
Tanana Uplands crystalline terrane to the south (fig. 4). 

During Quaternary time, there was up to 900 ft of 
downcutting by the Yukon River, and its tributaries and 
the Tertiary sediments are deeply incised. North of the Tin- 
tina Fault trench at localities on upper Washington, Ben, 
and Surprise Creeks, erosion and dip-slip or thrust faulting 
have exposed older rock that correlates to the Paleozoic and 
Precambrian marine sediments. A Cambrian age is ten- 
tatively assigned to the pre-Tertiary rocks due to Oldhamia 
fossils found in olive-green argillite and quartzite near 
Washington Creek (fig. 4). Tentative identification of the 
fossils as Oldhamia was made by Allison (1). The occurrence 
is comparable to Oldhamia reported elsewhere along the 




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Tintina Fault zone, as reported by Churkin (6). Rock 
resembling Precambrian Tindir volcanics was found pro- 
truding through the Tertiary section on Surprise Creek, and 
Paleozoic conglomerate occurs south of Boulder Creek. 
South of the Tintina Fault trench, the Tertiary rocks ap- 
pear to disconformably overlie crystalline terrane. Ex- 
posures, however, are poor. 



TINTINA FAULT TRENCH 

The Tertiary strata overlie and are transected by the 
Tintina Fault trench. This trench, at least 600 miles long, 
is a major regional, structural, and topographic feature in 
northwestern Canada and eastern Alaska. Elongated 
basins, one of which is the Eagle Trough, occur discon- 
tinuously along the length of the trench. Davies (7) 
estimated the fault trench to have 200 to 260 miles of right- 
lateral displacement. More recent estimates by Templeman- 
Kluit (20-21) have been slightly greater. Studies within the 
Canadian portion of the trench suggest displacement along 
subparallel interconnected faults rather than along a single 
fault plane (9, p. 2). The trench, where it transects the Eagle 
Trough, appears similarly complex with multiple faults, as 
exhibited on Coal Creek (fig. 5). Faults and other lineaments 
comprising the Tintina Fault trench within the Eagle 
Trough occur across a width of at least 5 to 10 miles. One 
of these lineaments is discussed in this report and is infor- 
mally referred to as the Bonanza Creek lineament. 

Although the Tintina Fault displays dominantly strike- 



slip offset, a minor component of dip-slip movement is lo- 
cally present. The fault escarpment and prominent butte 
near the upper terminus of placer mine workings of Coal 
Creek is evidence of dip-slip displacement. 

The ages of displacements on the Tintina Fault trench 
are poorly defined at present. Studies by U.S. and Cana- 
dian geologists (10, 20-21) conclude that most of the move- 
ment probably occurred in Late Cretaceous time. Dip-slip 
offset accompanying the strike-slip displacement resulted 
in elongated basins such as the Eagle Trough (9). These 
basins have been filled by coal-bearing sediments contain- 
ing Late Cretaceous (?) and early Tertiary age fossils (11-13). 
Fault escarpments and highly deformed Tertiary sediments 
and coal seams near Coal Creek indicate an episode of post- 
early Tertiary displacement. Similarly, to the southeast, 
in the Yukon Territory, 32 miles of post-Eocene movement 
that deformed Tertiary coal-bearing sediments within the 
Tintina Fault trench has been mapped (9, 15). This move- 
ment was presumed to be middle or late Tertiary in age. 
Geomorphic evidence of late Tertiary or early Quaternary 
right-lateral strike-slip movement elsewhere in the study 
area includes the prominent arc pattern of stream valleys. 
This feature occurs repetitiously on Woodchopper, Coal, and 
Sam Creeks, and possibly on the lower Charley River. Large 
nappelike features, 10 miles in diameter, such as in the 
vicinity of Drayham Creek to Flat Creek (fig. 4), and visi- 
ble in aerial photographs and on topographic maps, repre- 
sent the apparent result of strike-slip movement accom- 
panied by local thrusting and foreshortening south of the 
Tintina Fault. 



MINERAL PRODUCTION AND HISTORY 



Between 1898 and 1981, placer mines in the upper 
Yukon River region produced at least 229,632 tr oz Au and 
20,569 tr oz Ag (the latter as a refinery byproduct). Evidence 
of past unreported mining on some creeks suggests that the 
actual production total is somewhat higher. Following 
World War II the district had been inactive, but gold pro- 
duction resumed in the mid-1970's because of the increase 
in the price of gold. In 1981, about 20 to 30 people were 
working gold placer deposits in the upper Yukon River 
region. 

The following sections give brief descriptions of all 
creeks known to have produced gold or for which gold values 
have been reported. In these sections, comments pertain- 
ing to mining activity during the early years of this cen- 
tury are summarized from Mertie (11-13). Production data 
are derived from the Bureau's Minerals Availability System 
files. Mining claim location data are available from files 
of the Alaska Division of Geological and Geophysical Survey 
(ADGGS) 3 and map overlays prepared by the Bureau for 
each of Alaska's 153 quadrangles (23). The map location 
number or letter (as shown in figure 4) and ADGGS Kardex 4 
system file number for each creek is given at the end of each 
section. 

SAM CREEK 

No past production has been reported, but caved shafts 
are evidence of past prospecting. Above the mouth of Ben 



'Public Information Office, Box 80586, Fairbanks, AK 99708. 
'Reference to specific products does not imply endorsement by the Bureau 
of Mines. 



Creek, a total of 14 shafts encountered only scant gold. 
Below Ben Creek, gold appears to be derived from a lode 
source in the Ben Creek drainage. Alluvial gold was also 
found on the east fork (sample 68, appendix A). There are 
seven active claims on Sam Creek. Location 4 (fig. 4); 
ADGGS file 11. 



WILLOW CREEK 

Willow Creek is a headwater tributary to the Salcha 
River. No production has been reported. The most recent 
exploration and test mining was done in 1977. Abundant 
garnet in the gravels has made mining difficult. The source 
of gold is apparently quartz veins in the metamorphic rocks. 
There are seven inactive claims on the creek. Location 5 
(fig. 4); ADGGS file 28. 



FLAT CREEK 

No known production has been reported, but there are 
unverified past references to the occurrence of placer gold. 
No evidence of mining was found during this investigation, 
although gold was panned from the creek by Bureau in- 
vestigators (fig. 4). Claim locations are inactive. Location 
10 (fig. 4); ADGGS file 12. 

ROSEBUD CREEK 

Production has not been reported, but limited mining 




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has taken place, and exploration is continuing. The gold 
source is unknown. Gold is generally coarse and occurs on 
a clay bedrock. A sample of rust-coated placer gold consisted 
of highly rounded shot to 1/8 in across. Analysis indicated 
a fineness of 807. One claim was located in 1974. Location 
11 (fig. 4); ADGGS file 41. 



Creek. Production has not been reported, but Mertie (12-13) 
reported a placer gold occurrence. The source of the gold 
is unknown, although Mertie suggested that the Tertiary 
bedrock outcrops near the head of the valley may be the 
proximate host. Location 18 (fig. 4); ADGGS files 1, 6-8, and 
25. 



GROUSE CREEK 

The creek was reported by Brooks (5) to have been pros- 
pected as early as 1906 but with no known production. 
Bedrock is mapped as phyllite. Location 12 (fig. 4) is ten- 
tative; no ADGGS file. 



WEBBER CREEK 

No production has been reported, although field obser- 
vations suggest some mining occurred. Limited prospecting 
found minor gold values (25). The creek drains granitic 
bedrock at its headwaters. Phyllites and Tertiary conglom- 
erate outcrop further downstream. During this investiga- 
tion, previously unmapped conglomerate and mudstone 
were found on the east fork near a location where sparse 
gold was panned from the streambed. There are six inac- 
tive claims on the creek. Location 13 (fig. 4); ADGGS files 
5, 35, and 42-43. 



DOME CREEK 

Location 19 is a tributary to Washington Creek. There 
is no reported production, but intermittent mining occur- 
red in the years after the turn of the century (12-13). An 
unknown number of inactive claims are present on the 
creek. Location 19 (fig. 4); ADGGS files 14 and 17d. 



COLORADO CREEK 

Reported production in 1946 was 49 tr oz Au and 1 tr 
oz Ag. There was also limited, small-scale mining in 
previous years near the mouth of the creek. Further drill 
testing near the mouth of the creek was in progress in 1981. 
A galena-bearing quartz vein has been reported (5) in the 
creekbed near the junction with Coal Creek. An unknown 
number of inactive claims and four active claims are pres- 
ent on the creek. Location 20 (fig. 4); ADGGS files 9 and 41. 



SURPRISE CREEK 

Gold was discovered in 1907, and intermittent mining 
was reported for several years. Production is unknown, and 
no apparent traces of the past activity remain. Bedrock is 
Tertiary conglomerate and Tindir volcanics. An unknown 
number of inactive claims have been located. Location 14 
(fig. 4); ADGGS files 17b and 18a. 



ALDER CREEK 

No production has been reported, but some limited min- 
ing appears to have taken place. The source of the gold is 
unknown; however, sulfide-bearing tactite occurs further 
upstream. An unknown number of inactive mining claims 
have been located on the creek. Location 22 (fig. 4); ADGGS 
file 5. 



IRISH GULCH 

Mertie (12) reported that gold was found in the early 
1900's, but no production has been reported. Examination 
and panning in the lower half of the creek valley revealed 
no trace of gold. An unknown number of inactive claims 
have been located. Location 15 (fig. 4); ADGGS file 13a. 



EAGLE CREEK 

There are no reports of production. Gold was reported 
by Mertie (12-13) to be derived from the Tertiary con- 
glomerate. Location 16 (fig. 4); ADGGS file 18. 



DRAYHAM CREEK 

Placer gold occurrences were reported by Mertie (13), 
but no production is recorded. Gold was panned from 
Drayham Creek and three nearby streams during this in- 
vestigation (fig. 4). An unknown number of inactive claims 
are present. Location 17 (fig. 4); ADGGS file 13b. 

DOME CREEK 

Several creeks in the region are named Dome Creek. 
The creek discussed here is a tributary to Woodchopper 



FOURTH OF JULY CREEK 

Gold was discovered in 1898, and recorded production 
prior to 1939 was 6,624 tr oz Au and 736 tr oz Ag. No pro- 
duction has been reported since then. Exploration activity 
continued in 1978. According to Mertie (12-13), the 
paystreak is 400 to 500 ft wide and lies partially on a "clay 
bedrock" averaging $0.25 per bedrock foot at $35/tr oz Au. 
The gravel section is 6 to 15 ft thick and is overlain by 2 
to 7 ft of muck. Gold has an average fineness of 892; 
however, fineness varies up to 912 on the east side of the 
creek. Nuggets up to 0.5 tr oz have been recovered, although 
generally the gold is of a fine-grain size. 

Mertie speculated that the source of the gold is the con- 
glomerate that underlies the creek's upper headwaters. It 
appears that much of the gold production has been derived 
from the Union Gulch area. Exposures consisting of either 
weathered conglomerates or weakly cemented Quaternary 
terrace gravel near Union Gulch contain metamorphic 
clasts, chert, and vein quartz, from which a few specks of 
gold were panned. Higher bench gravels reportedly contain 
some gold, but little exploration has been done. Mertie 
(12-13) cited a shaft sunk on a bench along the west side 
of the valley which encountered gold values similar to those 
in ground being worked beneath the active channel. 

There are 25 claims on the creek. Location 23 (fig. 4); 
ADGGS files 19, 26, and 39. 



10 



RUBY CREEK 

Production reported for 1926 was 5 tr oz Au and 1 tr 
oz Ag, although it appears that more extensive mining has 
taken place. The proximate source of gold is the Tertiary 
conglomerate (12-13); however, a sample of silicified 
Paleozoic argillite creek rubble collected during this in- 
vestigation contained traces of gold. No outcrop could be 
viewed. There are at least two inactive claims on the creek. 
Location 24 (fig. 4); ADGGS files 20 and 29. 



SAWYER GULCH 

Production reported for 1918 was 6 tr oz Au and 2 tr 
oz Ag. The source of the gold is unknown. There are no 
known past mining claims. Location 25 (fig. 4) is tentative; 
no ADGGS file 

COAL CREEK 

Placer gold production reported through 1957 was 
94,493 tr oz Au and 9,668 tr oz Ag. The creek was first min- 
ed in the early 1900's with sluices and by drift mining. In 
1936, a 4-ft 3 bucket-line dredge was installed on a 400- to 
900-ft-wide paystreak; it operated into the 1940's. After a 
number of idle years, the dredge and sluice operation was 
reactivated in 1976. Between 1976 and 1978, an additional 
4,000 tr oz Au was produced, and 280,000 yd 3 of material 
was handled by a 12- to 25- person crew (25). In 1981, sluice 
box mining was in progress at a production rate of 2,000 
to 4,000 tr oz/yr. 

The gravel section occurs at varying depths from 5 to 
18 ft and requires thawing prior to mining. Locally, the 
gravel contains a high percentage of clay, which complicates 
recovery. The source of the gold is uncertain. There is a mix 
of bright angular and rounded, variably manganese-coated 
gold. Nuggets up to 2.5 tr oz have been found. The average 
fineness of past production is 897 (13). Estimates of drilled 
reserves provided by the operator in 1980 indicate that the 
section between the lower workings and the Yukon River 
contains a minimum of 21,000 tr oz Au. This paystreak lies 
at depths to 20 ft, but generally averages between 14 to 
18 ft. 

Ground formerly worked may also contain considerable 
unrecovered gold. An additional 16,000 tr oz Au is estimated 
by the operator to remain adjacent to the uppermost work- 
ings, but no economic reserves have been found upstream. 
Some gold is also reported by the operator in the higher 
alluvial benches, but there has been no detailed explora- 
tion. Apparently, unrelated placer gold occurrences also 
occur in the upper headwaters of the creek (location B on 
figure 4). Nearby is evidence of limited mining and water 
ditch development. 

Coal Creek is currently staked with 45 active claims. 
Locations 26 and B (fig. 4); ADGGS files 3, 10, and 40. 



BOULDER CREEK 

Drift mining was reported in 1935 and 1936. Produc- 
tion reported prior to 1951 was 334 tr oz Au and 42 tr oz 
Ag, although evidence of past mining suggests that these 
are only partial totals. Mining was undertaken in 1976 and 
1977 by an open-cut dozer operation. The source of the gold 
appears to be within the contact area of the Tertiary bedrock 
and adjacent quartz stockworks in the Permian bedrock. 



A sample of placer gold examined by the Bureau consisted 
of semirounded bright flakes up to 1/8 in across with a 
fineness of 903. There are four active claims on the creek. 
Location 27 (fig. 4); ADGGS file 2. 



MINERAL CREEK 

Production prior to 1947 was reported (13) to be 660 tr 
oz Au and 32 tr oz Ag with a gold fineness of 925. The creek 
has a paystreak about 100 ft wide and reportedly was first 
staked in 1898. Some gold and evidence of prospecting and 
mining activity have also been found on a small headwater 
tributary known as Alice Gulch. Nuggets weighing up to 
2.5 tr oz have been found. Limited mining between 1979 
and 1981 was undertaken on lower Mineral Creek. Min- 
ing claims on Mineral Creek are part of the group of min- 
ing claims located in the Woodchopper Creek valley. Loca- 
tion 28 (fig. 4); ADGGS files 15 and 17a, same as Woodchop- 
per Creek. 



WOODCHOPPER CREEK 

Woodchopper Creek was reportedly first mined in 1898. 
Production prior to 1963 was 117,654 tr oz Au and 9,783 
tr oz Ag, with an unusually high gold fineness of 933. 
Bucket-line dredging began in 1937. In 1981, operations 
were limited to exploration and mining near the confluence 
of Iron Creek. The paystreak is 600 to 700 ft wide, with 
gravel depths of 11 to 30 ft. These gravels contain a high 
percentage of granitic material and clay. The gold is 
generally coarse. Table 1, a mineralogic analysis of a sam- 
ple of dredge concentrate collected by the Bureau in 1970, 
notes the presence of cassiterite and wolframite. The source 
of the gold is primarily from the east side of the valley in 
the Mineral and Iron Creeks area and to some extent from 
the area just above the terminus of the workings. Claims 
are patented. Location 30 (fig. 4); ADGGS files 15 and 17a. 
Claims are also staked at the head of the valley (location 
C in figure 4), but there appears to have been no past 
mining. 



Table 1 .—Mineralogic analysis 1 of Woodchopper Creek 
placer concentrate, percent 

Minerals: 

Arsenopyrite Tr 

Cassiterite 2.0 

Feldspar 3 

Garnet 45.0 

Goethite and limonite 2 13.0 

Gold and mercury 3 

Hematite 1 

llmenite 2.0 

Platinum metals ND 

Pyrite 4 

Quartz 4.0 

Rutile 3.0 

Scheelite 7 

Sphene 2 

Staurolite 5.0 

Wolframite 4.0 

Rock fragments 19.0 

Unknown manganese minerals 1 .0 

Total 100.0 

ND Not detected. Tr Trace. 

'Optical microscope and optical emission spectroscopic methods. 

includes some garnet and rock fragments cemented by limonite. 

Source: W. Gnagy, petrologist, Bureau of Mines, Juneau, AK (retired). 



11 



IRON CREEK 

Production reported in 1926 was 9 tr oz Au and 1 tr oz 
Ag. Evidence of past activity indicates mining also occurred 
in more recent years. Prospecting and limited mining were 
undertaken from 1979 to 1981. The creek has unusually 
abundant ferricrete sediment, and gravels are composed of 
a high percentage of schist and quartz aggregate. Mining 
Claims on Iron Creek are part of the group of mining claims 
located in the Woodchopper Creek valley. Location 31 (fig. 
4); ADGGS files 15 and 17a, same as Woodchopper Creek. 



THANKSGIVING CREEK 

There have been unverified reports of placer gold values. 
Six placer claims were located in 1977. Location A (fig. 4); 
ADGGS file 44. 



NUGGET CREEK 

Production prior to 1939 was 1,772 tr oz Au and 302 tr 
oz Ag. Brooks (5) suggested the proximate source of gold 
is quartz stockwork in black slates. An unknown number 
of inactive claims are present on the creek. Location D (fig. 
4); ADGGS files 15, 17a. 



BEN CREEK 

Production reported in 1965 was 26 tr oz Au and 2 tr 
oz Ag, with a gold fineness of 896. Evidence of past mining 
activity suggests more gold was produced. Reportedly a 
right-limit bench deposit yielded 300 tr oz Au from a 70- 
by 250-ft cut, but this could not be verified. A sluice box- 
dozer operation was working in the 1977-79 period, but no 
production records are available. The proximate source of 
gold is reportedly the Tertiary conglomerate (12-13), but 
Cambrian(?) argillite and chlorite-altered quartzite with 
quartz stockwork and breccia were also found as rubble in 
the headwaters immediately upstream of the placer deposit. 
A sample of placer gold examined by the Bureau consisted 
of bright subangular flakes with a fineness of 908. Loca- 
tion E (fig. 4); no ADGGS file. 

BONANZA CREEK 

No production has been reported; however, there is 
evidence of prospect pits and possibly drift mining near the 
mouth of the creek. Gold could be panned in the creek 
gravels at this location and from a clay zone in the opposite 
bank of the Charley River (fig. 4). An exploratory drilling 
project on lower Bonanza Creek was conducted in 1936 (fig. 
6). The drilling indicated gold values were present but too 
low in grade and too inconsistently disbursed for dredge 
mining at the time. Location F (fig. 4); no ADGGS file. 



GOLD CONTENT IN PANNED CONCENTRATES 



The feasibility of using widespread panned concentrate 
sampling to determine favorable areas for gold deposition 
has been demonstrated by Boyle (3) near Keno Hill, Yukon 
Territory, Canada, and in an orientation study by Fischer 
(8) in the Telluride District, CO. In the latter study, non- 
mineralized, marginally mineralized, and known produc- 
ing areas were compared by analyses of concentrates. This 
technique was adopted in the upper Yukon River region 
with some refinements in sample preparation. In this in- 
vestigation, samples were further concentrated by heavy- 
liquid separations, which thereby enhanced the detention 
of gold. Analytical values were then corrected to reflect the 
actual recovery of gold in the original quantity of gravel. 
Bureau investigators collected and examined 162 samples 
from the locations shown in figure 7. 

Samples were obtained using a steel shovel to collect 
silty gravels from the channel center of smaller creeks or, 
in a few cases, from the leading edge of gravel bars on larger 
streams. A 14-in gold pan was filled and carefully panned 
until approximately 40 g of material remained. In the 
laboratory, the concentrated sample was air-dried and fur- 
ther concentrated in bromoform (sp gr 2.85). The plus 2.85-sp 
gr material was then sized on a 14-mesh screen, the over- 
size inspected for nuggets and discarded, and the undersize 
magnetically separated. The minus 14-mesh nonmagnetic 
fraction was dried and weighed. This material was not 
pulverized for analysis, because pulverizing could have 
resulted in the loss of flake gold. Instead, the entire split 
was taken into solution with aqua regia. Following the aqua 
regia digestion, gold was analyzed by an atomic absorption 
method, using a detection limit of 0.2 ppm. 5 



Sample splits were also analyzed for 24 elements by op- 
tical emission spectrography. These analyses are reported 
in a more comprehensive heavy-mineral survey of the 
Tanana Uplands by Barker (2). 

To reflect the regional pattern of background levels of 
gold, the actual gold recovery was calculated. This calcula- 
tion is possible where a standard size gravel sample and 
a similar procedure of concentration are used for each site. 
The recovery was determined by dividing the atomic ab- 
sorption analysis (A), in parts per million, by 1 million and 
then multiply ng the quotient by the weight (W) of the non- 
magnetic concentrate, in grams, times 1,000: 



R = 



1,000,000 



x 1.000W, 



5 Analyses performed by the Mineral Industry Research Laboratory, 
University of Alaska, Fairbanks, AK. 



where R = recovered gold, mg/(14-in) pan, 

A = analysis, ppm Au, 
and W = weight of minus 14-mesh, plus 2.85-sp gr non- 
magnetic concentrate, g. 

The final calculated value represents the weight (in 
milligrams) of minus 14-mesh gold that occurred in the 
original pan of creek gravel. This procedure eliminates the 
variability in gold concentration incurred when gold is 
determined as a percentage of contained heavy minerals. 
Gold values (in parts per million) will vary disproportionally 
relative to the amount of biotite, zircon, garnet, pyrite, and 
other heavy minerals. The percentage of these minerals in 
the heavy-mineral nonmagnetic concentrate will differ con- 
siderably from one site to another, particularly in a 
metamorphic-igneous terrane, and consequently often mask 
true background levels of gold. Normally, higher concen- 
trations of gold are encountered at depth in alluvial gravels 



12 



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w o o 
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13 




14 



100 



0) 



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0.04 0.08 0.12 0.16 0.20 



0.24 0.28 0.32 0.36 



GOLD, mg/pan 



FIGURE 8.— Histogram of gold content in 159 panned concentrates. (Values of 0.19 mg Au/pan and greater are anomalous.) 



or on bedrock. Samples collected in this study were collected 
from surface gravels only and therefore represented lower 
grade materials. 

For the purpose of this study, a value of 0.19 mg/pan 
was arbitrarily chosen as anomalous (fig. 8). Samples with 



equal or higher values are indicated on figure 4. This value 
(0.19 mg/pan) is equivalent to approximately $0.40/yd 3 at 
$500/tr oz. Analyzed and recovered gold values for the 162 
samples examined in the panned concentrate survey are 
listed in appendix A. 



MODE OF OCCURRENCE AND CHARACTER OF PLACER GOLD 



It has been suggested that the principal alluvial gold 
placer deposits of the upper Yukon River region formed from 
sparsely auriferous Tertiary conglomerate containing fossil 
placer gold (5. 12-13). The gold is believed to have been 
originally derived from the Tanana Uplands crystalline 
rocks, some miles to the south, south of the Tintina Fault. 
Most of the present economic alluvial placers occur within 
or downstream of the conglomerate. Within the areas of Ter- 
tiary bedrock, however, only certain creeks have been found 
to be substantially gold-bearing; others are notably barren 
or contain only traces. As for the creeks that are auriferous, 
it appears that gold is contributed only from certain zones 
of the valleys. In the case of Coal Creek, for example, placer 
gold comes primarily from the northern edge of the Tertiary 
bedrock in the vicinity of Boulder and Colorado Creeks (fig. 
5). There are other tributaries of Coal Creek, including those 



that drain Tertiary conglomerate, that have not been found 
to contain placer gold. On Fourth of July Creek, gold ap- 
pears to come principally from the Union and Ruby Creek 
areas. Throughout the upper Yukon region, erosion, soils, 
and vegetation cover allow very little outcrop, which makes 
stratigraphic examination difficult. Therefore, no positive 
correlation of the gold to the Tertiary sediments or any other 
lode source has yet been made. 

Other similarities exist among the placers of the upper 
Yukon River region. Green and red clay is often abundant 
within the paystreaks. Concentrates contain wolframite, 
cassiterite, and abundant garnet. Galena grains or galena- 
bearing vein material has been observed on several creeks 
including Coal, Colorado, Placer, and Rosebud Creeks. 

Several types of gold are found in the placers. The gold 
particles usually occur as either well-rounded, tarnished, 



15 









=^:sr,rTr^^^^ 



largest piece 

iron and manganese coatings from Rosebud Creek 



16 



variably iron- and manganese-stained blebs; or as bright, 
subangular to subrounded scales, flakes, and nuggets with 
quartz occasionally attached. On some creeks, both types 
of gold are present. On Coal Creek, a portion of the gold 
occurs as angular to subangular nuggets with a sugary- 
trot hv surface texture (fig. 9, A and B). Several angular gold 
nuggets recovered from Coal Creek in 1980, from the clay 
zones near the uppermost workings, were found attached 
and enveloped around garnet, black sand, and quartz par- 
ticles. These contrasting forms of placer gold indicate multi- 
ple origins. They are quite evident in the field and have 
been noted by all who have worked in the region. 

Sainsbury (18), who examined the Coal and Woodchop- 
per Creeks area in 1966, noted a distinct change in the gold 
character. Rounded, stained gold from the Tertiary con- 
glomerate area contrasted with bright, flaky gold from the 
clay zones further downstream. He also noted dredge con- 
centrate containing nuggets intergrown with angular vein 
quartz but coated with manganese stain. 

Fineness values of gold samples from the upper Yukon 
River region (table 2) are relatively high compared to those 
of other areas in interior Alaska. (See gold fineness data 
given by Smith (19)). Although most of the fineness values 
are in the 895 to 915 range, there are several notable ex- 
ceptions, with values that closely approximate those of one 
or the other of the two types of gold discussed above. Gold 
from Rosebud Creek is mostly of the highly rounded, tar- 
nished type and has a much lower fineness of 807. Gold of 
the subangular, bright scaly type, at sample location 54 (fig. 
7), had an unusually high value of 970. Based on visual ex- 
amination of the other samples, it is likely that the fineness 
range of 895 to 915 resulted from assays of concentrates 



Table 2.— Fineness of upper Yukon River region gold samples 

Location ££* Sample description 

SAMPLES COLLECTED BY BUREAU OF MINES'!? 
Boulder Creek . . 903 Bright gold, some pieces moderately to 

well-rounded, from placer cut on lower 

portion ol creek. 
Rosebud Creek 807 Highly rounded shot with variable Fe and 

Mn staining; from lower creek. 
Ben Creek 908 Moderately rounded bright flakes and 

bright subrounded shot; from sluice box 

concentrate. 

Do 864 Bright rounded to subrounded flakes. 

Coal Creek 914 Subangular bright flakes and rounded 

small nuggets; from upper area of placer 

workings, 1979 cleanup. 
Mineral Creek 897 Bright flake gold, some with Mn coatings; 

from 1980 cleanup near mouth of creek. 
Washington Creek 3 . . 970 Very bright, subangular scales to flakes; 2 

assays, sample 55 (fig. 10). 
Bonanza Creek 855 Bright subrounded specks and scales; 

sample 61 (fig. 7). 
Charley River 4 845 Subrounded flat nuggets and scales; as 

sample 62 (fig. 7). 

DATA FROM REFERENCE 13 
Fourth of July Creek 892 No description, av of 24 assays. 

Ben Creek 896 No description, 1 assay. 

Coal Creek 897 No description, av of 16 assays. 

Mineral Creek 925 No description, av of 13 assays. 

Woodchopper Creek . 932 No description, av of 6 assays. 

'Of these samples, only those from Washington and Bonanza Creeks and 
the Charley River were among the 162 samples discussed in this report (and 
listed in appendix A). 

2 Fineness determinations provided by N. Veach, mineralogist, Alaska Divi- 
sion of Geological and Geophysical Surveys, Fairbanks, AK. 

3 Unnamed tributary. 

"Clay zone. 

containing both of these texture types, and thus reflected 
a combination of the higher grade angular, scaly gold and 
the rounded gold with its lower fineness value. 



SIGNIFICANCE OF BONANZA CREEK LINEAMENT ZONE FOR PLACER GOLD 



The Tintina Fault trench comprises numerous faults 
and fracture zones across its width of 5 to 10 miles. Most 
of these are poorly exposed, if they are exposed at all, and 
are only discernable as alignments of topographic and 
vegetation features. The Bonanza Creek lineament, as in- 
terpreted from aerial photographs 6 (figs. 4-5), was examined 
in detail because very nearly all of the gold production in 
the upper Yukon River region has been derived from creeks 
immediately downstream of it. 

The Bonanza Creek lineament, informally named in this 
report because of its alignment with Bonanza Creek, is a 
zone intermittently traceable from near Woodchopper Creek 
eastward to Washington Creek that may extend to Fourth 
of July Creek. On both Coal and Woodchopper Creeks, the 
lineament zone (fig. 5) is characterized by probable low-level 
hydrothermal alteration, as indicated by varicolored 
massive green, red, and white clay, bleached and decom- 
posed sedimentary rock, quartz stockworks, and boxworks. 
Gypsum and slickensides are also common features. On 
Woodchopper and Coal Creeks, silicification and breccia- 
tion occur in the resistant Permian or older bedrock to the 
immediate north, whereas angular quartz masses are found 
in the clay zones that border the bleached and sheared Ter- 
tiary strata to the south. The saline-evaporite mineral 
dawsonite [NaAlC0 3 (OH) 2 ], which can be associated with 



6 False-color high-altitude imagery, flight lines 67-69, available for inspec- 
tion at the Geophysical Institute, Room 501, University of Alaska, Fair- 
banks, AK. 



low-level hydrothermal alteration, was identified in sheared 
Tertiary mudstone. 7 A sample of this material also con- 
tained traces of gold (0.01 tr oz/st). Fragments of sheared 
coal contain stockwork veinlets of quartz, siderite, and 
pyrite. Coal from near the lineament was visibly vitreous. 
A sample collected on Coal Creek was found to have a 
vitrinite reflectance of 0.48; another nearby coal sample 
gave a reflectance of 0.65. These values are somewhat 
higher than would be expected for interior Alaska lignitic 
Tertiary coals, which typically have reflectance values of 
0.2 to 0.3, suggesting minor thermal upgrading. 

X-ray diffraction analyses of clay samples from the 
lineament zone on Coal Creek indicated a mineral 
assemblage of quartz, gypsum, potassium feldspar, 
muscovite, kaolinite, and variable amounts of chlorite, 
which, when present, imparts a bright green color. Because 
of weathering of the clay, only tentative confirmation of 
these clays as being hydrothermal is possible. Similar clay 
is found aligned with and along the Bonanza Creek linea- 
ment where it crosses Boulder and Sam Creeks, at the very 
lower end of Cheese Creek, on the Charley River, and in 
creek float on Bonanza Creek. Placer gold can be found at 
all these locations. Elsewhere, the lineament zone is totally 
covered by vegetation. 

The Coal Creek placer deposit, according to the operator 
there, has a drill-indicated paystreak approximately 700 



'Analysis by X-ray diffraction; performed by T. C. Mowatt, geologist. 
Bureau of Mines, Juneau, AK 



17 



to 900 ft wide downstream of the projected trace of the linea- 
ment. Upstream of the projected trace, no mining has been 
attempted, and the paystreak sharply reduces to 300 ft in 
width and a lower tenor. Little drilling has been done fur- 
ther upstream, and there has been no lode gold exploration. 
A sample of partially cleaned Coal Creek placer concen- 
trates taken from downstream of the lineament was found 



to commonly contain angular or frothy-textured gold par- 
ticles (fig 9, A and B) and abundant grains of conchoidal- 
shaped, gray, friable metallics identified as the halides of 
cotunnite (PbCl 2 ) and laurionite [Pb(OH)Cl] 9 In several 
observed instances, the lead minerals formed around grains 
of gold. 



OTHER LOCATIONS CONTAINING GOLD 



Several other locations (not listed in the "Mineral Pro- 
duction and History" section) in the upper Yukon River 
region have been reported, or were found during this proj- 
ect, to contain gold. (See sites of anomalous gold values on 
figure 4.) None of these sites, however, have produced any 
significant quantity of gold, and none are currently being 
prospected. 

In the Placer Creek valley, a tributary to upper 
Washington Creek, sphalerite and galena were found, oc- 
curring as disseminated sulfides in the conglomerate 
matrix. (See figure 4, location labeled "Lead-zinc sulfides," 
near location 24.) An analyzed sample contained 1.0% Pb, 
2.7% Zn, a trace of gold (less than 0.01 tr oz), and 0.37% 
As. The occurrence was found in rubble and could not be 
assessed further. 

Bedrock in the vicinity of sample 54 (fig. 10) was mapped 
in an attempt to delineate the lode source of the placer gold 
found there, which has an unusually high fineness. Bedrock 
on the north side of the valley comprises Tertiary mudstone 
and lignite, whereas bedrock on the south side consists of 
olive-green argillite and quartzite which is silicified along 
fractures. A thrust fault contact is interpreted to parallel 
the valley. HydrothermaK?) quartz stockwork has 
permeated the silicified sediments. The quartz veinlets con- 
tain accessory magnetite and particularly well-developed 
chlorite along the selvage zones. Chlorite is pervasive in 



the silicified groundmass and typically coats the quartz 
grains. Some samples contain over 50% chlorite. No visi- 
ble gold could be observed in hand specimens, and two 
analyzed samples were barren. 

Similar olive-green rock was also seen in the creek float 
on the gold placer creeks of Ruby, Webber, Woodchopper, 
Ben, Boulder, and Surprise. Six random samples of this 
material, one composited from each creek, were fire-assayed 
for gold, but gold was detected only in the sample from Ruby 
Creek. That analysis indicated 0.01 tr oz/st Au. A neutron- 
activation analysis of another split of the Ruby Creek sam- 
ple indicated 0.32 tr oz/st Au. 

A group of gold anomalies was found during the panned 
concentrate survey in the vicinity of the eastern Charley 
River batholith. Free gold was observed in the concentrates. 
The source of the gold is unknown; however, abundant vein 
quartz in the creeks suggests a local hydrothermal origin. 

Anomalous gold values in panned concentrates occur 
in several other areas within or downstream of Tertiary 
bedrock. These include the east forks of Webber and Sam 
Creeks (figure 7, samples 12 and 68), nearby Cultas Creek 
(sample 69), and several sites on Derwent Creek (samples 
146 and 149). Sample 51, which was taken 1 mile south of 
the creek where sample 54 was collected (fig. 10), was par- 
ticularly anomalous for gold (appendix A). The origin of the 
gold is unknown. 



PLATINUM ASSOCIATION 



Mertie, in 1942 (13, pp. 257-259), reported unusually 
high platinum concentrations, thought to be alloyed in 
placer gold. His analyses of gold from Woodchopper Creek 
indicated 0.42% Pt; Broken Neck and Fourth of July Creeks 
yielded 0.20% Pt and 0.28% Pt, respectively. All of the 
Bureau's gold samples listed in table 2 were analyzed for 
platinum by a fire assay-spectrographic method, but no 
platinum was detected, even at trace levels. Mertie's 1942 
analyses reporting significant platinum in placer gold may 



be suspect, given the analytical procedures for platinum 
available at that time. Rare grains of platinum-metal alloys 
do occur in placer concentrates and were found during this 
investigation on Boulder Creek (sample 74) and near 
Washington Creek (sample 55). On Boulder Creek, the 
panned concentrate contained grains of chromite and a 
single grain of osmiridium 9 with an osmium-to-iridium ratio 
of 5:1. 9 Pan sample 55 contained a grain of ferroplatinum. 9 



DISCUSSION AND RECOMMENDATIONS 



The upper Yukon River region has produced a signifi- 
cant amount of placer gold from operations dating back to 
1898. Most of this production has come from dredges on Coal 
and Woodchopper Creeks, where additional dredging 
ground still remains. Many other creeks are known to con- 
tain gold. 

The gold placers of the upper Yukon River region may 
have formed, at least in part, from local hydrothermal 
sources. A notable feature of the placers is the spatial 



association of most known deposits with the Bonanza Creek 
lineament. Previous suggestions that the gold in the Wood- 
chopper and Coal Creeks area is reworked from Tertiary 
conglomerates and originally derived from the present 
Tanana Uplands crystalline terrane to the south are incon- 



8 Analysis by X-ray diffraction; performed by W.S. Roberts, geologist, 
Bureau of Mines, Juneau. AK. 

'Scanning electron microscope analysis by J. Sjoberg, mineralogist, Bureau 
of Mines, Reno, NV. 



18 



Wi 



/ 



»-5 
»-5 




LEGEND 



Tertiary nonmarine sediments 



Paleozoic-Precambrian marine sedimentary sequence; 
includes olivine-green argillites, quartzites, and maroon 
and green argillites 



?— Inferred contact, queried where uncertain 

a_a Thrust fault 

O 50 Panned concentrate sample site 

# 55 Anomalous gold content in panned concentrate 



Scale, miles 
Base adapted from U.S.G.S. 1:63,360 Charley River quadrangles CA-3 and B-3) 



FIGURE 10.— Sample locations 50 through 56, Washington Creek. (Location of this figure is shown in figure 7.) 



19 



sistent with the presence of flake and subangular gold and 
nuggets as large as 2.5 tr oz, such as have been found on 
Mineral Creek. Furthermore, no significant gold placers 
have been found over the straight-line distance of 7 or more 
miles between these two areas. Similarly, there are no 
known nearby sources of the garnets and friable heavy 
minerals such as native bismuth found on Rosebud Creek, 
galena found on Coal and Colorado Creeks, and wolframite 
and cassiterite found on Woodchopper Creek. Placers de- 
rived from distant bedrock sources would not likely contain 
these minerals in the abundance found in the study area. 

Alluvial gold from the upper Yukon River region ap- 
pears to have several origins, and the present placers are 
an apparent mix of both reworked ancient placers and low- 
temperature(?) hydrothermal gold. The first of these types 
of gold is rounded, oxide-coated, shotty-type gold that is like- 
ly being reworked from ancient Tertiary fossil placers. Pro- 
bably the fossil placers originally derived gold from near- 
by upland sources now displaced to the west by the Tintina 
Fault, prior to much of the sedimentation that is now fill- 
ing the Eagle Trough. The similar westerly arc-shaped 
feature of Woodchopper, Coal, and Sam Creeks, and possibly 
the Charley River, indicates right-lateral displacement (fig. 
4). Continuing post-early Tertiary right-lateral movement 
along the Tintina Fault, which appears to have occurred 
in stages, has displaced the upland gold sources to the west 
and has resulted in the abandonment of alluvial gold 
placers. 

If allowance is made for some 50 miles of displacement 
along the Tintina fault zone, a plausible source of placer 
Tertiary gold in the upper Yukon River region could be the 
71-million-yr-old Circle meta-igneous complex (in the Cir- 
cle Quadrangle, west of the study area shown in figure 4). 
Middle- to late-Tertiary displacements on the order of 30 
miles have been indicated along the Tintina Fault in 
Canada (9). It is noteworthy that a spatial correlation of 
the Woodchopper-Coal-Ben Creeks area and the Portage- 
Deadwood-Crooked Creeks area in the Circle district can 
be made by a reconstruction of fault movement. Wolframite- 
and cassiterite-bearing placers on Deadwood Creek align 
with Woodchopper Creek, where these minerals are also 
found. Placer occurrences associated with the Tertiary 
bedrock region are limited to the north side of the main 



trace of the Tintina Fault, whereas the Circle Hot Springs 
district has produced gold only to the south of the fault. 

Low-temperature(?) hydrothermal veins and shear 
zones, such as the Bonanza Creek lineament zone, possibly 
account for the second type of gold. This type is typified by 
generally bright, subangular to subrounded flat flakes, 
scales, and nuggets with high fineness values and, par- 
ticularly, the angular, sugary-textured gold. This latter tex- 
ture type and its apparent higher fineness suggest that an 
authigenic process may be involved. 

The evidence of gold in primary sources, particularly 
in altered shear zones such as the Bonanza Creek zone, 
should be thoroughly examined with respect to both placer 
and lode deposits. Bonanza Creek, where past drift mining 
is in evidence, is particularly favorable since it aligns 
parallel to the lineament instead of merely crossing it (figs. 
4 and 6). The Webber and Thanksgiving Creeks areas war- 
rant evaluation for both abandoned paleo-alluvial channels 
and fault-zone-related placers. Other linear geologic 
features, such as the inferred thrust fault near sample 54, 
may also be mineralized. Trenching or shallow drilling to 
intersect the fault zone will be necessary. Further 
characterization of the geochemical and geothermal history 
(e.g., hot springs activity) of altered fault zones should also 
be made. Exploration targets should address the fault zones 
with potential for gold deposits in both Tertiary and base- 
ment Cambrian(?) bedrock. Similarly, the presence of lead, 
zinc, arsenic, and iron sulfides in the conglomerate, such 
as on Colorado and Placer Creeks, suggests gold may also 
be deposited in this association. 

The anomalous gold values found in creeks draining into 
the Charley River, particularly east of Twin Mountain and 
extending downstream of Bonanza Creek, suggest the 
possibility of placer enrichment in the Charley River flood 
plain. The gold anomalies at sample locations 68 and 69 
possibly indicate gold enrichment along the southern ex 
tent of the Tertiary sediments. 

High-level terrace gravels may locally contain placer 
gold. There have been unverified local reports of placer gold 
from such gravels on both Coal and Fourth of July Creeks. 
Mineral and Iron Creeks may also contain some high-level 
terrace gold. 



CONCLUSIONS 



The predominant Tertiary-age sediments of the Eagle 
Trough are well-rounded chert-, quartzite-, and quartz- 
conglomerate; coal-bearing mudstone; and sandstone that 
were deposited by the ancestral Yukon River or other major 
southwesterly flowing drainages. The detritus probably 
derived from the marine Paleozoic and Precambrian rocks 
to the east and north, which were eroded during the Eocene 
development of the Nation Arch. They can be expected to 
be barren of alluvial gold. 

Conversely, less common conglomerate composed of 
meta-igneous sediments from the Tanana Uplands 
crystalline terrane to the south may contain ancient placer 
gold and thereby account for part of the gold in the present 
alluvial placers. To date, however, there is no positive 
evidence that any Tertiary conglomerates contain ancient 
placer gold. 



Examination and fineness analyses of gold concentrates 
indicate that other origins of gold are responsible for placers. 
There is a close spatial correlation of the significant placer 
deposits and the Bonanza Creek lineament. Alteration and 
mineralizing processes associated with the lineament zone 
may be at least partially responsible for the placers. 

With the exception of Coal and Woodchopper Creeks, 
the region is poorly explored due to the extensive soil and 
vegetation cover and permafrost. A heavy-mineral survey 
of 162 panned concentrate samples found 26 to contain 
anomalous levels of gold. The region is favorable for the 
discovery of additional reserves of both lode and placer gold, 
and exploration along the Bonanza Creek lineament is par- 
ticularly suggested. 



20 



REFERENCES 



1. Allison, C. (Univ. AK Museum). Private communication, 1981; 
available upon request from J. Barker, BuMines, Fairbanks, AK. 

2. Barker, J. C. Mineral Deposits of the Tanana-Yukon Uplands. 
A Summary Report. BuMines OFR 88-78, 1978, 33 pp. 

3. Boyle, R. W., and C. F. Gleeson. Gold in the Heavy Mineral 
Concentrates of Stream Sediments, Keno Hill Area, Yukon Ter- 
ritory. Can. Geol. Survey Paper 71-51, 1972, 8 pp. 

4. Brabb, E. E., and M. Churkin, Jr. Geologic Map of the Charley 
River Quadrangle, East-Central Alaska. U.S. Geol. Surv. Misc. 
Geol. Inv. Map 1-573, 1969; 1 sheet; scale, 1:250,000. 

5. Brooks, A. H. The Circle Precinct, Alaska. Ch. K in Report 
on Progress of Investigations of Mineral Resources of Alaska in 
1906. U.S. Geol. Surv. Bull. 314, 1907, pp. 187-204. 

6. Churkin, M., Jr., and E. E. Brabb. Occurrence and 
Stratigraphic Significance of Oldhamia, a Cambrian Trace Fossil 
in East-Central Alaska. Ch. D in Geological Survey Research 1965. 
U.S. Geol. Surv. Prof. Pap. 525-D, 1965, pp. D120-D124. 

7. Davies, W. E. The Tintina Trench and Its Reflection on the 
Structure of the Circle Area, Yukon-Tanana Upland, Alaska. Paper 
in Proceedings of 24th International Geological Congress. Int. Geol. 
Congr., 1972, pp. 211-216. 

8. Fischer, R. P., and F. S. Fisher. Interpreting Pan-Concentrate 
Analyses of Stream Sediments in Geochemical Exploration for Gold. 
U.S. Geol. Surv. Circ. 592, 1968, 9 pp. 

9. Hughes, J. D., and D. G. F. Long. Geology and Coal Resource 
Potential of Early Tertiary Strata Along Tintina Trench, Yukon 
Territory. Can. Geol. Surv. Paper 79-32, 1980, 21 pp. 

10. Jones, D. L., N. J. Silberling, H. C. Berg, and G. Plafker. Map 
Showing Tectonostratigraphic Terranes of Alaska, Columnar Sec- 
tions, and Summary Descriptions of Terranes. U.S. Geol. Surv. 
Open File Rep. 81-792, 1981; 2 sheets; scale, 1:250,000. 

11. Mertie, J. B., Jr. The Yukon-Tanana Region, Alaska. U.S. 
Geol. Surv. Bull. 872, 1937, 276 pp. 

12. Gold Placers of the Fortymile, Eagle, and Cir- 
cle Districts. Ch. C in Mineral Resources of Alaska, Report on Prog- 
ress of Investigations in 1936. U.S. Geol. Surv. Bull. 897 -C, 1938, 
pp. 133-261. 

13. . Tertiary Deposits of the Eagle-Circle District, 

Alaska. Ch. D in Mineral Resources of Alaska, Report on Progress 
of Investigations in 1938. U.S. Geol. Surv. Bull. 917-D, 1942, pp. 
213-263. 



14. Miller, D. J., T. G. Payne, and G. Gryc. Geology of Possible 
Petroleum Provinces in Alaska. U.S. Geol. Surv. Bull. 1094, 1959, 
131 pp.; 6 sheets. 

15. Milner, M., and D. B. Craig (Can. Dep. Indian and Northern 
Affairs). Coal in the Yukon. Unpubl. manuscript, 27 pp; available 
upon request from Jim Moran, Dep. Indian and Northern Affairs, 
Whitehorse, YT, Can. 

16. Pewe, T. L., L. Burbank, and L. R. Mayo. Multiple Glacia- 
tion of the Yukon-Tanana Upland, Alaska. U.S. Geol. Surv. Misc. 
Geol. Inv. Map 1-507, 1967; scale, 1:500,000. 

17. Prindle, L. M., and J. B. Mertie, Jr. Gold Placers Between 
Woodchooper and Fourth of July Creeks, Upper Yukon River. Ch. 
G in Mineral Resources of Alaska, Report on Progress of Investiga- 
tions in 1937. U.S. Geol. Surv. Bull. 520-G, 1912, pp. 201-210. 

18. Sainsbury, C. L., A. L. Clark, and A. L. Sutton. Private com- 
munication, 1980; available upon request from C. L. Sainsbury, 
Air Samplex, Inc., Denver, CO. 

19. Smith, P. S. Fineness of Gold from Alaska Placers. Ch. C in 
Mineral Resources of Alaska, Report on Progress of Investigations 
in 1937. U.S. Geol. Surv. Bull. 910-C, 1941, pp. 147-191. 

20. Tempelman-Kluit, D. J. Stratigraphic and Structural Rela- 
tions Between the Selwyn Basin, Pelly-Cassiar Platform, and 
Yukon Crystalline Terrane in the Pelly Mountains, Yukon. Can. 
Geol. Surv. Paper 77-1A, 1977, pp. 223-227. 

21. Tempelman-Kluit, D. J., S. P. Gordey, and B. C. Read. 
Stratigraphic and Structural Studies in the Pelly Mountains, 
Yukon Territory. Can. Geol. Surv. Paper 76-1A, 1976, pp. 97-106. 

22. Turner, D. L., D. Grybeck, and F. H. Wilson. Radioactive 
Dates from Alaska— A 1975 Compilation. AK Div. Geol. Geophys. 
Surv. Spec. Rep. 10, 1975, 6 pp. 

23. U.S. Bureau of Mines, Staff. Alaska 1:250,000 Scale 
Quadrangle Map Overlays Showing Mineral Deposit Locations, 
Principal Minerals, Number and Type of Claims. BuMines OFR 
20-73, 1973, 153 overlays. 

24. Weber, F. R. Glacial Geology of the Yukon-Tanana Upland- 
A Progress Report. Ch. in Glaciation in Alaska, ed. by R. M. Thor- 
son and T. D. Hamilton. Univ. AK Museum Occasional Paper 2, 
1983, 100 pp. 

25. Wolff, E. (Director, Miner. Ind. Res. Lab., Univ. AK, retired). 
Private communication, 1979; available upon request from J. 
Barker, BuMines, Fairbanks, AK. 



APPENDIX A.— GOLD IN HEAVY-MINERAL CONCENTRATES 



21 



Gold 



Sample 



Minus 14-mesh 

nonmagnetic Content, Recover- 
conc, g pp m et j m g 



Rock types present in creek rubble, estimated % x 0.1 
(See end of tabulation for explanation of abbreviations.) 



1 . . 

2 .. 

3 .. 

4 .. 

5 .. 

6 .. 

7 . . 

8 .. 

9 .\ 

10 . 

11 . 

12 . 

13 . 

14 . 

15 . 

16 . 

17 . 

18 . 

19 . 

20 . 

21 . 

22 . 

23 . 
24'. 

25 . 

26 . 

27 . 

28 . 

29 . 

30 . 
31 2 . 

32 . 

33 . 

34 . 

35 . 

36 . 

37 . 

38 . 

39 . 

40 . 

41 . 

42 . 

43 . 

44 . 
453. 

46 . 

47 . 

48 . 

49 . 

50 . 

51 . 

52 . 
53". 
54". 
55 . 

56". 

57 . 

58 . 

59 . 
603. 
61". 
62". 
63». 

64 . 

65 . 

66 . 
67". 

68 . 

69 . 

70 . 

71 . 

72 . 

73 . 
749. 

75 . 

76 . 

77 . 

78 . 

79 . 

80 . 

81 . 
823. 

83 . 

84 . 

85 . 



13.710 

22.851 

24.120 

7.060 

2.744 

14.825 

6.885 

1.690 

16.662 

15.004 

15.702 

30.285 

6.316 

11.901 

3.301 

31.257 

1.026 

4.452 

11.471 

1.741 

1.637 

10.101 

.546 

9.261 

2.822 

7.735 

3.563 

4.745 

.676 

.166 

4.976 

4.351 

1.479 

.450 

.974 

.646 

4.164 

5.868 

6.791 

7.241 

4.569 

.978 

NA 

NA 

5.805 

2.473 

3.345 

2.295 

.322 

3.058 

15.568 

NA 

NA 

NA 

3.650 

NA 

.095 

6.985 

1.871 

3.189 

NA 

NA 

14.484 

11.403 

2.480 

3.654 

1.500 

23.701 

10.807 

26.191 

23.450 

18.854 

10.025 

NAp 

7.145 

3.161 

8.030 

3.655 

75.473 

4.511 

11.495 

8.710 

18.694 

8.193 

31 .674 



ND 
ND 
ND 
.32 
22.00 

1.2 

7.34 
ND 
ND 
ND 

4.2 
12 
ND 
.2 
ND 
ND 
ND 
ND 
ND 
ND 
ND 
ND 

1.75 
ND 
ND 

1.12 
ND 
ND 
ND 
ND 
ND 
ND 
ND 
ND 
ND 
ND 
ND 
.69 

4.4 

9.8 

1.5 
ND 
ND 
ND 

2.6 
ND 
ND 
ND 
ND 
ND 
270 
ND 
NA 
ND 
300 


NA 
ND 

8.2 

6.2 
139.00 
NA 
NA 

2.0 

1.4 
ND 
ND 
ND 
22 
83 

3.4 

1.1 
ND 
ND 
NAp 

5.4 
29 

1.0 
140 
ND 
13 
ND 
.43 
198.00 
ND 
.40 



ND 3 

ND 3 

ND 1 
0.002 1 
.060 - 
.018 - 
.050 - 

ND - 

ND - 

ND - 
.066 1 
.363 

ND 
.002 

ND 

ND 

ND 

ND 

ND 

ND 

ND 

ND 
.001 

ND 

ND 
.009 

ND 

ND 

ND 

ND 

ND 

ND 

ND 

ND 

ND 

ND 

ND 1 
.004 2 
.030 2 
.071 5 
.007 

ND - 

ND - 

ND - 
.015 - 

ND - 

ND 1 

ND . 

ND - 

ND - 
4.203 - 

ND - 
=6 
6297.1 



10.95 — 
?2 — 

ND — 
.057 — 
.012 — 
.443 — 
'6 — 

15.2 — 
.029 .5 
.016 — 
ND — 
ND — 
ND — 
.521 — 
.897 — 
.089 — 
.026 — 
ND — 
ND — 
NAp NAp 
.039 
.092 
.008 
.512 
ND 
.059 
ND 
.004 
3.701 
ND 
.013 



Tr 
2 



5 — 



Tr 
2 






— 2 — 



2 2 — 
— 1 — 

Tr 1 — 






— Tr — — — 



— Tr 



3 — — — 2 

2 — — 1 3 

1 — — 2 3 

— — — 2 4 



.5 — — 






_ 2 — — — 



2 — 
— .5 






2 

Tr 

1 



— — — 2 






6 

10 



.5 — — 






— .5 






— 4 
2 — 
2 2 
5 — 

— 1 

— .5 

— 1 



Tr 

1 

1 

2 

1 

2 

1 

1 

2 



— .5 



2 
Tr 



4.5 



Tr 

5 

1 



2 
3 

4.5 

7 
3 



1 

2 

1.5 

1 

.5 
Tr 

2 
1 



— — 3 — 



— 3 — - 
.5 1 — - 

11—- 

1 — — Ti 

— — Tr 1 
_ 4 _ _ 

— 2 — - 
5 2—- 



3 

— 1 

— 1 



.5 — — 
2 — — 



— 2 
2 - 



1 
1 

2 

NAp NAp NAp NAp NAp NAp NAp NAp 
1 



Tr 


1 


.5 


3 


— 


Tr 


1 


2 


1 


3 
2 


— 


.5 


1 


2 


— 


4 


Tr 






1 



— — — 2 






— — — — 8 



1 
3 
Tr 
5 



2 
1 
4 
3 
4 
2 
4 
NAp NAp NAp NAp NAp NAp NAp NAp 

1 — — 1 — 1 — 6 

2 1 — — 1 — — 2 
__ — — 3 4 — — 
— 1 — — 2 3 — — 

2 2 — — — 1 — — 



2 — — 



2 — — 2 



1 






3 Tr — 

— 2 — 

— 4 — 



See explanatory notes at end of tabulation. 



22 



Minus 14-mesh Gold 

Sample nonmagnetic Content, Recover- . 

cone, g p prn e( j, m g 



Rock types present in creek rubble, estimated % x 0.1 
(See end of tabulation for explanation of abbreviations.) 



86 

87 

88V 

89 

90 

91 . 

92 

93 . 

94 

95 . 

96 . 

97 . 

98 . 



100 . 
101 
102 . 
103 
104 . 
105 

106 . 

107 .. 

108 . . 
109 

110 .. 

111 . 

112 . . 

113 . . 

114 .. 

115 .. 

116 .. 

117 . 

118 . . 
119" 
120" . 

121 . . 

122 . . 

123 . . 

124 . . 

125 .. 

126 .. 

127 .. 

128 . 

129 . 

130 . . 

131 .. 

132 . 

133 .. 

134 . 

135 .. 

136 .. 

137 .. 

138 .. 

139 . . 

140 .. 

141 .. 
142 

143 .. 

144 .. 

145 . 
146'2 . 
147 .. 
148' 3 . 

149 . . 

150 . . 

151 .. 

152 . . 

153 .. 

154 .. 

155 .. 

156 . . 

157 .. 

158 . 

159 .. 

160 .. 

161 . 

162 . 



50.119 
10320 
18.574 
17.132 
44.710 
18.694 
43 443 
33.440 
21.855 

4.923 
12.662 
37.290 
31.025 
22.186 

5.684 
12.203 

6.179 

2.963 
40.268 

3.351 

3.155 
20.943 

2.389 
12.385 
14.907 

5.564 
11.443 

9.670 
15.919 

1 1 .229 
10.155 
11.556 
19.659 
21.465 
28.660 
12.651 
15.111 
11.187 
22.116 
28.286 

1.622 

2.834 

4.870 

9.772 

2.430 

2.442 

44.371 

7.117 

33.704 

29.747 

18.654 

27.567 

1 1 .075 

19.759 

1 1 .230 
3.828 
4.577 

NA 

11.610 

2.708 

8.690 

1.145 

3.349 

5.413 

6.504 

2.154 

12.373 

12.280 

6.107 

35.515 

32.462 

5.947 

18.746 

10.959 

4.695 

20.680 

10.927 



120 00 
.2 
ND 
ND 
NO 
ND 
ND 
4.40 
ND 
ND 
ND 
ND 
.59 
ND 
ND 
ND 
.60 
.22 
ND 
.20 
ND 
ND 
.32 
ND 
ND 
ND 

11 
2.2 
.46 
.84 
ND 
ND 
ND 
ND 
ND 

53 
ND 
ND 
5.7 
ND 

59 
ND 

76 

65 
800 

22 

52 
ND 
ND 
ND 

32 
7.4 
ND 
ND 

29 

65 

26 
ND 

11 
8.6 
110 
ND 

33 

54 

12 

26 

42 
5.7 

50 
4.7 
ND 
ND 
ND 
ND 
ND 
2 
ND 



2 

Tr 



6.014 — — 
">.12 — — 
ND — — 
ND — 3 
ND — — 
ND - — 
ND — — 

.147 — — 
ND — — 
ND — — 
ND — - 
ND — — 

.018 — - 
ND — — 
ND — — 
ND — — 

.004 — — 

.001 — — 
ND — — 

.001 — — 
ND — — 
ND — — 

.001 — — 
ND — — 
ND — — 
ND — — 

.126 — — 

.021 — — 

.007 — — 

.009 — — 
ND — — 
ND — — 
ND — — 
ND — — 
ND — — 
0.671 - 
ND 
ND 

.126 
ND 

.096 
ND 

.370 

.635 
1.944 

.054 
2.307 
ND 
ND 
ND 

.597 

.204 
ND 
ND 

.326 

.249 

.119 
ND 

.128 

.025 

.956 
ND 

.110 

.292 

.078 

.056 

.520 

.070 

.305 

.167 
ND 
ND 
ND 
ND 
ND 
ND 
ND 



3 - 



Tr 3 






2 

1 

Tr 

2 

3 

2 

3 

3 

2 

5 

2 

2 

4 

3 

1 

2 



12 
1 

A 

s 



— 1 

— 1 

— 1 



9 

4 
10 
10 

4 
10 

9 
10 

5 






7—2 

— — 4 



— 1 

— 1 



4 — 

5 — 

— 2 

— 1 



1 — — 



1 1 

2 1 

1 — 

2 Tr 



— 1 1 



— .5 

— 6 

— Tr 

— 3 



6 — 
2 — 






5 — — — 



.5 
Tr 

1 

1 

1 

Tr 

1 

1 

2 

1 

1 

1 

1 

2 

2 

2 

3 

Tr 

3 

1 

4 

2 

2 

2 



.5 — 



— — Tr 

— — 2 

— — 2 

— — 3 

— — 2 

— — 3 



3 
8 

Tr 

4 

4 

4 

1 

7 

7 

2 
1 



— — — — Tr 



— 5 

— 6 

— 4 

— 4 
3 — 
2 — 



— 1 

— Tr 

— 2 






— 1 



6 — 



1 4 

2 3 

— 7 

Tr 5 

5 — 



— 2 






— — — — Tr Tr 



— Rock type not present. NA Not analyzed. NAp Not applicable. 

'Burned shale also present. 
2 Hematite also present, 0.1%. 
3 No rock types, only sands. 

4 Manually separated gold, samples not analyzed by atomic absorption methods. 
^Flakes. 
6 ln 30-pan bulk sample. 

Rock type abbreviations 



ND Not detected. Tr Trace. 

7 Specks. 

°Clay, sideritic sandstone. 

9 Boulder. 
10 5.5-pan sample. 
"Traces of grit also present. 
12 Clay also present, 0.1%. 
"Mostly sand, possible phyllite rock type present. 



A. . . Slate 
C... Chert 
D. . . Dolomite 
E . . . Calcite 



G. 
H.. 



Gneiss 

Shale, silt- 
stones, fine- 
grain elastics 



I . . . Schist 
L. . . Limestone 
O. . . Conglomerate 
P . . . Phyllite 



NOTE.— Recovered gold values of 0.19 mg/pan were arbitrarily chosen as anomalous. 



Q. . . Quartz 
R . . . Argillite 
S . . . Sandstone 
T. . . Quartzite 



W. . . Intrusive — felsic 
X . . . Intrusive — mafic 
Z. . . Volcanic— mafic 



APPENDIX B.— SAMPLE IDENTIFICATION KEY 



23 



(Sample numbers used in this report related to field numbers referenced in 
previous Bureau open file report (2)) 



, Field 

Sam P le number 

1 KD1807 

2 KD1805 

3 KD1801 

4 KD1643 

5 KD8147 

6 KD1653 

7 KD1794 

8 KD1661 

9 KD1659 

10 KD8232 

11 KD1791 

12 KD8152 

13 KD1673 

14 KD1671 

15 KD1675 

16 KD1669 

17 KD8234 

18 KD1786 

19 KD1784 

20 KD8262 

21 KD1695 

22 KD1763 

23 KD8249 

24 KD1744 

25 KD8109 

26 KD8161 

27 KD8270 

28 KD1752 

29 KD8272 

30 KD8277 

31 KD8252 

32 KD1722 

33 KD1720 

34 KD1717 

35 KD8256 

36 KD8259 

37 KD1757 

38 KD1759 

39 KD1712 

40 KD1708 

41 KD1706 



„ Field 

Sam P le number 

42 KD8378 

43 KD10658 

44 KD10662 

45 KD8373 

46 KD8375 

47 KD1703 

48 K01701 

49 KD8383 

50 KD8367 

51 KD8370 

52 KD10630 

53 KD10634 

54 KD8368 

55 KD8101 

56 KD2971 

57 KD8388 

58 KD1772 

59 KD1689 

60 KD2968 

61 KD12379 

62 KD12439 

63 KD1778 

64 KD8156 

65 KD2965 

66 KD2964 

67 KD8240 

68 KD8415 

69 KD8390 

70 KD8392 

71 KD8413 

72 KD8417 

73 KD8419 

74 KD1809 

75 KD8236 

76 KD8238 

77 KD8422 

78 UP8425 

79 UP338 

80 UP8002 

81 UP8004 

82 UP279 



Co ,„ Field 

Sam P le number 

83 UP341 

84 UP278 

85 UP271 

86 UP801 1 

87 UP10610 

88 UP345 

89 UP343 

90 UP298 

91 UP289 

92 UP301 

93 UP304 

94 UP66 

95 UP59 

96 UP449 

97 UP4 

98 UP51 

99 UP146 

100 UP149 

101 UP220 

102 UP222 

103 UP934 

104 UP936 

105 UP938 

106 UP880 

107 UP883 

108 UP885 

109 UP70 

110 UP6 

111 UP370 

112 UP367 

113 UP362 

114 UP8054 

115 UP8206 

116 UP8016 

117 UP8018 

118 UP8020 

119 UP237 

120 UP235 

121 UP8215 

122 UP8213 

123 UP8023 



o i Field 

Sam P' e number 

124 UP8025 

125 UP8027 

126 UP8029 

127 UP8032 

128 UP8217 

129 UP8221 

130 UP8036 

131 UP8040 

132 UP8223 

133 UP95 

134 UP97 

135 UP99 

136 UP8227 

137 UP8043 

138 UP8046 

139 UP8049 

140 UP8126 

141 UP353 

142 UP360 

143 KD10650 

144 UP357 

145 UP8300 

146 UP8342 

147 UP8344 

148 UP8347 

149 UP8311 

150 UP8309 

151 UP8351 

152 UP8355 

153 UP8358 

154 UP8305 

155 UP8361 

156 UP8303 

157 UP296 

158 UP294 

159 UP291 

160 UP248 

161 UP243 

162 UP241 



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